A Long Term Evolution-Advanced (Long Term Evolution-Advanced, LTE-A for short) system is a further evolved and enhanced system based on a 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP for short) Long Term Evolution (Long Term Evolution, LTE for short) system. In the LTE-A system, to meet the peak data rate required by the International Telecommunications Union for the fourth-generation communications technologies, a carrier aggregation (Carrier Aggregation, CA for short) technology is introduced, which is also referred to as a spectrum aggregation (Spectrum Aggregation) technology or bandwidth extension (Bandwidth Extension) technology. In carrier aggregation, spectra of two or more component carriers (Component Carrier) are aggregated to obtain a wider transmission bandwidth. The spectra of component carriers may be adjacent continuous spectra or nonadjacent spectra in the same band, or even discontinuous spectra in different bands. In an LTE Release 8 or 9 (Release-8/9, Rel-8/9 for short) system, a user equipment (User Equipment, UE for short) can access only one of the component carriers to receive or transmit data; in an LTE-A system, however, a user equipment can access multiple component carriers simultaneously according to its capabilities and service requirements to receive or transmit data.
To support dynamic scheduling, downlink multiple input multiple output (Multiple Input Multiple Output, MIMO for short) transmission, hybrid automatic repeat request and other technologies, the user equipment needs to feed back uplink control information (Uplink Control Information, UCI for short) to a base station. The uplink control information UCI may include channel state information (Channel State Information, CSI for short) and hybrid automatic repeat request acknowledgment (Hybrid Automatic Repeat Request-Acknowledgment, HARQ-ACK for short) information. The hybrid automatic repeat request acknowledgment information may be referred to briefly as acknowledgment (Acknowledgment, ACK for short)/negative acknowledgement (Negative Acknowledgment, NACK for short) information.
In LTE-A, due to introduction of the carrier aggregation technology, when a user equipment accesses multiple downlink component carriers simultaneously to receive downlink data, the user equipment needs to feed back its channel state information CSI in the uplink direction for each downlink component carrier, and also needs to feed back its hybrid automatic repeat request acknowledgment information HARQ-ACK in the uplink direction for data scheduled on each downlink component carrier. On the one hand, the user equipment generally needs to determine the reporting time of periodic CSI of each carrier according to the reporting period and the subframe offset of each carrier configured by high layer signaling. On the other hand, the user equipment needs to feed back hybrid automatic repeat request acknowledgment information HARQ-ACK when detecting a physical downlink shared channel (Physical Downlink Shared Channel, PDSCH for short) or a physical downlink control channel (Physical Downlink Control Channel, PDCCH for short) indicative of semi-persistent scheduling release (Semi-persistent Scheduling Release, SPS for short). Therefore, in an LTE-A carrier aggregation scenario, the user equipment needs to report both channel state information and hybrid automatic repeat request acknowledgment information in one uplink subframe. The channel state information to be reported may correspond to one or more downlink carriers, and the hybrid automatic repeat request acknowledgment information to be reported may also correspond to one or more downlink carriers.
In a current LTE carrier aggregation system, when only periodic CSI needs to be transmitted, a physical uplink control channel (Physical Uplink Control Channel, PUCCH for short) of format 2 (Format 2) may be used for transmission. When only hybrid automatic repeat request acknowledgment information HARQ-ACK needs to be transmitted, a PUCCH of format 1a or format 1b or format 3 may be used for transmission. However, when both the periodic CSI and the hybrid automatic repeat request acknowledgment information HARQ-ACK need to be transmitted in one subframe, in most cases, the periodic CSI is discarded, and only the hybrid automatic repeat request acknowledgment information HARQ-ACK is transmitted.
In the carrier aggregation system, to support simultaneous transmission of the periodic CSI and the hybrid automatic repeat request acknowledgment information HARQ-ACK, the user equipment may obtain a PUCCH of format 3 according to high layer signaling indicated semi-statically, to transmit the periodic CSI and the HARQ-ACK. However, in the foregoing method, once a PUCCH resource of format 3, which is reserved semi-statically, is assigned to a UE, the resource is occupied by the UE no matter whether the UE needs to transmit the periodic CSI and the HARQ-ACK simultaneously, which leads to high resource overhead used to transmit uplink control information and leads to low resource utilization.